/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

/*
 * Source:
 * http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/test/tck/JSR166TestCase.java?revision=1.90
 * (We have made some trivial local modifications (commented out
 * uncompilable code).)
 */

package com.google.common.util.concurrent;

import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static java.util.concurrent.TimeUnit.NANOSECONDS;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.CodeSource;
import java.security.Permission;
import java.security.PermissionCollection;
import java.security.Permissions;
import java.security.Policy;
import java.security.ProtectionDomain;
import java.security.SecurityPermission;
import java.util.Arrays;
import java.util.Date;
import java.util.NoSuchElementException;
import java.util.PropertyPermission;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.Semaphore;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicReference;

import junit.framework.AssertionFailedError;
import junit.framework.TestCase;

/**
 * Base class for JSR166 Junit TCK tests. Defines some constants, utility methods and classes, as
 * well as a simple framework for helping to make sure that assertions failing in generated threads
 * cause the associated test that generated them to itself fail (which JUnit does not otherwise
 * arrange). The rules for creating such tests are:
 *
 * <ol>
 *   <li>All assertions in code running in generated threads must use the forms {@link #threadFail},
 *       {@link #threadAssertTrue}, {@link #threadAssertEquals}, or {@link #threadAssertNull}, (not
 *       {@code fail}, {@code assertTrue}, etc.) It is OK (but not particularly recommended) for
 *       other code to use these forms too. Only the most typically used JUnit assertion methods are
 *       defined this way, but enough to live with.
 *   <li>If you override {@link #setUp} or {@link #tearDown}, make sure to invoke {@code
 *       super.setUp} and {@code super.tearDown} within them. These methods are used to clear and
 *       check for thread assertion failures.
 *   <li>All delays and timeouts must use one of the constants {@code SHORT_DELAY_MS}, {@code
 *       SMALL_DELAY_MS}, {@code MEDIUM_DELAY_MS}, {@code LONG_DELAY_MS}. The idea here is that a
 *       SHORT is always discriminable from zero time, and always allows enough time for the small
 *       amounts of computation (creating a thread, calling a few methods, etc) needed to reach a
 *       timeout point. Similarly, a SMALL is always discriminable as larger than SHORT and smaller
 *       than MEDIUM. And so on. These constants are set to conservative values, but even so, if
 *       there is ever any doubt, they can all be increased in one spot to rerun tests on slower
 *       platforms.
 *   <li>All threads generated must be joined inside each test case method (or {@code fail} to do
 *       so) before returning from the method. The {@code joinPool} method can be used to do this
 *       when using Executors.
 * </ol>
 *
 * <p><b>Other notes</b>
 *
 * <ul>
 *   <li>Usually, there is one testcase method per JSR166 method covering "normal" operation, and
 *       then as many exception-testing methods as there are exceptions the method can throw.
 *       Sometimes there are multiple tests per JSR166 method when the different "normal" behaviors
 *       differ significantly. And sometimes testcases cover multiple methods when they cannot be
 *       tested in isolation.
 *   <li>The documentation style for testcases is to provide as javadoc a simple sentence or two
 *       describing the property that the testcase method purports to test. The javadocs do not say
 *       anything about how the property is tested. To find out, read the code.
 *   <li>These tests are "conformance tests", and do not attempt to test throughput, latency,
 *       scalability or other performance factors (see the separate "jtreg" tests for a set intended
 *       to check these for the most central aspects of functionality.) So, most tests use the
 *       smallest sensible numbers of threads, collection sizes, etc needed to check basic
 *       conformance.
 *   <li>The test classes currently do not declare inclusion in any particular package to simplify
 *       things for people integrating them in TCK test suites.
 *   <li>As a convenience, the {@code main} of this class (JSR166TestCase) runs all JSR166 unit
 *       tests.
 * </ul>
 */
abstract class JSR166TestCase extends TestCase
{
    private static final boolean useSecurityManager = Boolean.getBoolean("jsr166.useSecurityManager");

    protected static final boolean expensiveTests = Boolean.getBoolean("jsr166.expensiveTests");

    /**
     * If true, report on stdout all "slow" tests, that is, ones that take more than profileThreshold
     * milliseconds to execute.
     */
    private static final boolean profileTests = Boolean.getBoolean("jsr166.profileTests");

    /**
     * The number of milliseconds that tests are permitted for execution without being reported, when
     * profileTests is set.
     */
    private static final long profileThreshold = Long.getLong("jsr166.profileThreshold", 100);

    @Override
    protected void runTest() throws Throwable
    {
        if (profileTests) runTestProfiled();
        else super.runTest();
    }

    protected void runTestProfiled() throws Throwable
    {
        long t0 = System.nanoTime();
        try
        {
            super.runTest();
        }
        finally
        {
            long elapsedMillis = (System.nanoTime() - t0) / (1000L * 1000L);
            if (elapsedMillis >= profileThreshold)
                System.out.printf("%n%s: %d%n", toString(), elapsedMillis);
        }
    }

    //     /**
    //      * Runs all JSR166 unit tests using junit.textui.TestRunner
    //      */
    //     public static void main(String[] args) {
    //         if (useSecurityManager) {
    //             System.err.println("Setting a permissive security manager");
    //             Policy.setPolicy(permissivePolicy());
    //             System.setSecurityManager(new SecurityManager());
    //         }
    //         int iters = (args.length == 0) ? 1 : Integer.parseInt(args[0]);

    //         Test s = suite();
    //         for (int i = 0; i < iters; ++i) {
    //             junit.textui.TestRunner.run(s);
    //             System.gc();
    //             System.runFinalization();
    //         }
    //         System.exit(0);
    //     }

    //     public static TestSuite newTestSuite(Object... suiteOrClasses) {
    //         TestSuite suite = new TestSuite();
    //         for (Object suiteOrClass : suiteOrClasses) {
    //             if (suiteOrClass instanceof TestSuite)
    //                 suite.addTest((TestSuite) suiteOrClass);
    //             else if (suiteOrClass instanceof Class)
    //                 suite.addTest(new TestSuite((Class<?>) suiteOrClass));
    //             else
    //                 throw new ClassCastException("not a test suite or class");
    //         }
    //         return suite;
    //     }

    //     /**
    //      * Collects all JSR166 unit tests as one suite.
    //      */
    //     public static Test suite() {
    //         return newTestSuite(
    //             ForkJoinPoolTest.suite(),
    //             ForkJoinTaskTest.suite(),
    //             RecursiveActionTest.suite(),
    //             RecursiveTaskTest.suite(),
    //             LinkedTransferQueueTest.suite(),
    //             PhaserTest.suite(),
    //             ThreadLocalRandomTest.suite(),
    //             AbstractExecutorServiceTest.suite(),
    //             AbstractQueueTest.suite(),
    //             AbstractQueuedSynchronizerTest.suite(),
    //             AbstractQueuedLongSynchronizerTest.suite(),
    //             ArrayBlockingQueueTest.suite(),
    //             ArrayDequeTest.suite(),
    //             AtomicBooleanTest.suite(),
    //             AtomicIntegerArrayTest.suite(),
    //             AtomicIntegerFieldUpdaterTest.suite(),
    //             AtomicIntegerTest.suite(),
    //             AtomicLongArrayTest.suite(),
    //             AtomicLongFieldUpdaterTest.suite(),
    //             AtomicLongTest.suite(),
    //             AtomicMarkableReferenceTest.suite(),
    //             AtomicReferenceArrayTest.suite(),
    //             AtomicReferenceFieldUpdaterTest.suite(),
    //             AtomicReferenceTest.suite(),
    //             AtomicStampedReferenceTest.suite(),
    //             ConcurrentHashMapTest.suite(),
    //             ConcurrentLinkedDequeTest.suite(),
    //             ConcurrentLinkedQueueTest.suite(),
    //             ConcurrentSkipListMapTest.suite(),
    //             ConcurrentSkipListSubMapTest.suite(),
    //             ConcurrentSkipListSetTest.suite(),
    //             ConcurrentSkipListSubSetTest.suite(),
    //             CopyOnWriteArrayListTest.suite(),
    //             CopyOnWriteArraySetTest.suite(),
    //             CountDownLatchTest.suite(),
    //             CyclicBarrierTest.suite(),
    //             DelayQueueTest.suite(),
    //             EntryTest.suite(),
    //             ExchangerTest.suite(),
    //             ExecutorsTest.suite(),
    //             ExecutorCompletionServiceTest.suite(),
    //             FutureTaskTest.suite(),
    //             LinkedBlockingDequeTest.suite(),
    //             LinkedBlockingQueueTest.suite(),
    //             LinkedListTest.suite(),
    //             LockSupportTest.suite(),
    //             PriorityBlockingQueueTest.suite(),
    //             PriorityQueueTest.suite(),
    //             ReentrantLockTest.suite(),
    //             ReentrantReadWriteLockTest.suite(),
    //             ScheduledExecutorTest.suite(),
    //             ScheduledExecutorSubclassTest.suite(),
    //             SemaphoreTest.suite(),
    //             SynchronousQueueTest.suite(),
    //             SystemTest.suite(),
    //             ThreadLocalTest.suite(),
    //             ThreadPoolExecutorTest.suite(),
    //             ThreadPoolExecutorSubclassTest.suite(),
    //             ThreadTest.suite(),
    //             TimeUnitTest.suite(),
    //             TreeMapTest.suite(),
    //             TreeSetTest.suite(),
    //             TreeSubMapTest.suite(),
    //             TreeSubSetTest.suite());
    //     }

    public static long SHORT_DELAY_MS;
    public static long SMALL_DELAY_MS;
    public static long MEDIUM_DELAY_MS;
    public static long LONG_DELAY_MS;

    /**
     * Returns the shortest timed delay. This could be reimplemented to use for example a Property.
     */
    protected long getShortDelay()
    {
        return 50;
    }

    /**
     * Sets delays as multiples of SHORT_DELAY.
     */
    protected void setDelays()
    {
        SHORT_DELAY_MS = getShortDelay();
        SMALL_DELAY_MS = SHORT_DELAY_MS * 5;
        MEDIUM_DELAY_MS = SHORT_DELAY_MS * 10;
        LONG_DELAY_MS = SHORT_DELAY_MS * 200;
    }

    /**
     * Returns a timeout in milliseconds to be used in tests that verify that operations block or time
     * out.
     */
    long timeoutMillis()
    {
        return SHORT_DELAY_MS / 4;
    }

    /**
     * Returns a new Date instance representing a time delayMillis milliseconds in the future.
     */
    Date delayedDate(long delayMillis)
    {
        return new Date(System.currentTimeMillis() + delayMillis);
    }

    /**
     * The first exception encountered if any threadAssertXXX method fails.
     */
    private final AtomicReference<Throwable> threadFailure = new AtomicReference<>(null);

    /**
     * Records an exception so that it can be rethrown later in the test harness thread, triggering a
     * test case failure. Only the first failure is recorded; subsequent calls to this method from
     * within the same test have no effect.
     */
    public void threadRecordFailure(Throwable t)
    {
        threadFailure.compareAndSet(null, t);
    }

    @Override
    public void setUp()
    {
        setDelays();
    }

    /**
     * Extra checks that get done for all test cases.
     *
     * <p>Triggers test case failure if any thread assertions have failed, by rethrowing, in the test
     * harness thread, any exception recorded earlier by threadRecordFailure.
     *
     * <p>Triggers test case failure if interrupt status is set in the main thread.
     */
    @Override
    public void tearDown() throws Exception
    {
        Throwable t = threadFailure.getAndSet(null);
        if (t != null)
        {
            if (t instanceof Error) throw (Error) t;
            else if (t instanceof RuntimeException) throw (RuntimeException) t;
            else if (t instanceof Exception) throw (Exception) t;
            else
            {
                AssertionFailedError afe = new AssertionFailedError(t.toString());
                afe.initCause(t);
                throw afe;
            }
        }

        if (Thread.interrupted()) throw new AssertionFailedError("interrupt status set in main thread");
    }

    /**
     * Just like fail(reason), but additionally recording (using threadRecordFailure) any
     * AssertionFailedError thrown, so that the current testcase will fail.
     */
    public void threadFail(String reason)
    {
        try
        {
            fail(reason);
        }
        catch (AssertionFailedError t)
        {
            threadRecordFailure(t);
            fail(reason);
        }
    }

    /**
     * Just like assertTrue(b), but additionally recording (using threadRecordFailure) any
     * AssertionFailedError thrown, so that the current testcase will fail.
     */
    public void threadAssertTrue(boolean b)
    {
        try
        {
            assertTrue(b);
        }
        catch (AssertionFailedError t)
        {
            threadRecordFailure(t);
            throw t;
        }
    }

    /**
     * Just like assertFalse(b), but additionally recording (using threadRecordFailure) any
     * AssertionFailedError thrown, so that the current testcase will fail.
     */
    public void threadAssertFalse(boolean b)
    {
        try
        {
            assertFalse(b);
        }
        catch (AssertionFailedError t)
        {
            threadRecordFailure(t);
            throw t;
        }
    }

    /**
     * Just like assertNull(x), but additionally recording (using threadRecordFailure) any
     * AssertionFailedError thrown, so that the current testcase will fail.
     */
    public void threadAssertNull(Object x)
    {
        try
        {
            assertNull(x);
        }
        catch (AssertionFailedError t)
        {
            threadRecordFailure(t);
            throw t;
        }
    }

    /**
     * Just like assertEquals(x, y), but additionally recording (using threadRecordFailure) any
     * AssertionFailedError thrown, so that the current testcase will fail.
     */
    public void threadAssertEquals(long x, long y)
    {
        try
        {
            assertEquals(x, y);
        }
        catch (AssertionFailedError t)
        {
            threadRecordFailure(t);
            throw t;
        }
    }

    /**
     * Just like assertEquals(x, y), but additionally recording (using threadRecordFailure) any
     * AssertionFailedError thrown, so that the current testcase will fail.
     */
    public void threadAssertEquals(Object x, Object y)
    {
        try
        {
            assertEquals(x, y);
        }
        catch (AssertionFailedError t)
        {
            threadRecordFailure(t);
            throw t;
        }
        catch (Throwable t)
        {
            threadUnexpectedException(t);
        }
    }

    /**
     * Just like assertSame(x, y), but additionally recording (using threadRecordFailure) any
     * AssertionFailedError thrown, so that the current testcase will fail.
     */
    public void threadAssertSame(Object x, Object y)
    {
        try
        {
            assertSame(x, y);
        }
        catch (AssertionFailedError t)
        {
            threadRecordFailure(t);
            throw t;
        }
    }

    /**
     * Calls threadFail with message "should throw exception".
     */
    public void threadShouldThrow()
    {
        threadFail("should throw exception");
    }

    /**
     * Calls threadFail with message "should throw" + exceptionName.
     */
    public void threadShouldThrow(String exceptionName)
    {
        threadFail("should throw " + exceptionName);
    }

    /**
     * Records the given exception using {@link #threadRecordFailure}, then rethrows the exception,
     * wrapping it in an AssertionFailedError if necessary.
     */
    public void threadUnexpectedException(Throwable t)
    {
        threadRecordFailure(t);
        t.printStackTrace();
        if (t instanceof RuntimeException) throw (RuntimeException) t;
        else if (t instanceof Error) throw (Error) t;
        else
        {
            AssertionFailedError afe = new AssertionFailedError("unexpected exception: " + t);
            afe.initCause(t);
            throw afe;
        }
    }

    /**
     * Delays, via Thread.sleep, for the given millisecond delay, but if the sleep is shorter than
     * specified, may re-sleep or yield until time elapses.
     */
    static void delay(long millis) throws InterruptedException
    {
        long startTime = System.nanoTime();
        long ns = millis * 1000 * 1000;
        for (; ; )
        {
            if (millis > 0L) Thread.sleep(millis);
            else // too short to sleep
                Thread.yield();
            long d = ns - (System.nanoTime() - startTime);
            if (d > 0L) millis = d / (1000 * 1000);
            else break;
        }
    }

    /**
     * Waits out termination of a thread pool or fails doing so.
     */
    void joinPool(ExecutorService exec)
    {
        try
        {
            exec.shutdown();
            assertTrue(
                    "ExecutorService did not terminate in a timely manner",
                    exec.awaitTermination(2 * LONG_DELAY_MS, MILLISECONDS));
        }
        catch (SecurityException ok)
        {
            // Allowed in case test doesn't have privs
        }
        catch (InterruptedException ie)
        {
            fail("Unexpected InterruptedException");
        }
    }

    /**
     * Checks that thread does not terminate within the default millisecond delay of {@code
     * timeoutMillis()}.
     */
    void assertThreadStaysAlive(Thread thread)
    {
        assertThreadStaysAlive(thread, timeoutMillis());
    }

    /**
     * Checks that thread does not terminate within the given millisecond delay.
     */
    void assertThreadStaysAlive(Thread thread, long millis)
    {
        try
        {
            // No need to optimize the failing case via Thread.join.
            delay(millis);
            assertTrue(thread.isAlive());
        }
        catch (InterruptedException ie)
        {
            fail("Unexpected InterruptedException");
        }
    }

    /**
     * Checks that the threads do not terminate within the default millisecond delay of {@code
     * timeoutMillis()}.
     */
    void assertThreadsStayAlive(Thread... threads)
    {
        assertThreadsStayAlive(timeoutMillis(), threads);
    }

    /**
     * Checks that the threads do not terminate within the given millisecond delay.
     */
    void assertThreadsStayAlive(long millis, Thread... threads)
    {
        try
        {
            // No need to optimize the failing case via Thread.join.
            delay(millis);
            for (Thread thread : threads) assertTrue(thread.isAlive());
        }
        catch (InterruptedException ie)
        {
            fail("Unexpected InterruptedException");
        }
    }

    /**
     * Checks that future.get times out, with the default timeout of {@code timeoutMillis()}.
     */
    void assertFutureTimesOut(Future future)
    {
        assertFutureTimesOut(future, timeoutMillis());
    }

    /**
     * Checks that future.get times out, with the given millisecond timeout.
     */
    void assertFutureTimesOut(Future future, long timeoutMillis)
    {
        long startTime = System.nanoTime();
        try
        {
            future.get(timeoutMillis, MILLISECONDS);
            shouldThrow();
        }
        catch (TimeoutException success)
        {
        }
        catch (Exception e)
        {
            threadUnexpectedException(e);
        }
        finally
        {
            future.cancel(true);
        }
        assertTrue(millisElapsedSince(startTime) >= timeoutMillis);
    }

    /**
     * Fails with message "should throw exception".
     */
    public void shouldThrow()
    {
        fail("Should throw exception");
    }

    /**
     * Fails with message "should throw " + exceptionName.
     */
    public void shouldThrow(String exceptionName)
    {
        fail("Should throw " + exceptionName);
    }

    /**
     * The number of elements to place in collections, arrays, etc.
     */
    public static final int SIZE = 20;

    // Some convenient Integer constants

    public static final Integer zero = new Integer(0);
    public static final Integer one = new Integer(1);
    public static final Integer two = new Integer(2);
    public static final Integer three = new Integer(3);
    public static final Integer four = new Integer(4);
    public static final Integer five = new Integer(5);
    public static final Integer six = new Integer(6);
    public static final Integer seven = new Integer(7);
    public static final Integer eight = new Integer(8);
    public static final Integer nine = new Integer(9);
    public static final Integer m1 = new Integer(-1);
    public static final Integer m2 = new Integer(-2);
    public static final Integer m3 = new Integer(-3);
    public static final Integer m4 = new Integer(-4);
    public static final Integer m5 = new Integer(-5);
    public static final Integer m6 = new Integer(-6);
    public static final Integer m10 = new Integer(-10);

    /**
     * Runs Runnable r with a security policy that permits precisely the specified permissions. If
     * there is no current security manager, the runnable is run twice, both with and without a
     * security manager. We require that any security manager permit getPolicy/setPolicy.
     */
    public void runWithPermissions(Runnable r, Permission... permissions)
    {
        SecurityManager sm = System.getSecurityManager();
        if (sm == null)
        {
            r.run();
            Policy savedPolicy = Policy.getPolicy();
            try
            {
                Policy.setPolicy(permissivePolicy());
                System.setSecurityManager(new SecurityManager());
                runWithPermissions(r, permissions);
            }
            finally
            {
                System.setSecurityManager(null);
                Policy.setPolicy(savedPolicy);
            }
        }
        else
        {
            Policy savedPolicy = Policy.getPolicy();
            AdjustablePolicy policy = new AdjustablePolicy(permissions);
            Policy.setPolicy(policy);

            try
            {
                r.run();
            }
            finally
            {
                policy.addPermission(new SecurityPermission("setPolicy"));
                Policy.setPolicy(savedPolicy);
            }
        }
    }

    /**
     * Runs a runnable without any permissions.
     */
    public void runWithoutPermissions(Runnable r)
    {
        runWithPermissions(r);
    }

    /**
     * A security policy where new permissions can be dynamically added or all cleared.
     */
    public static class AdjustablePolicy extends java.security.Policy
    {
        Permissions perms = new Permissions();

        AdjustablePolicy(Permission... permissions)
        {
            for (Permission permission : permissions) perms.add(permission);
        }

        void addPermission(Permission perm)
        {
            perms.add(perm);
        }

        void clearPermissions()
        {
            perms = new Permissions();
        }

        @Override
        public PermissionCollection getPermissions(CodeSource cs)
        {
            return perms;
        }

        @Override
        public PermissionCollection getPermissions(ProtectionDomain pd)
        {
            return perms;
        }

        @Override
        public boolean implies(ProtectionDomain pd, Permission p)
        {
            return perms.implies(p);
        }

        @Override
        public void refresh()
        {
        }
    }

    /**
     * Returns a policy containing all the permissions we ever need.
     */
    public static Policy permissivePolicy()
    {
        return new AdjustablePolicy
                // Permissions j.u.c. needs directly
                (
                        new RuntimePermission("modifyThread"),
                        new RuntimePermission("getClassLoader"),
                        new RuntimePermission("setContextClassLoader"),
                        // Permissions needed to change permissions!
                        new SecurityPermission("getPolicy"),
                        new SecurityPermission("setPolicy"),
                        new RuntimePermission("setSecurityManager"),
                        // Permissions needed by the junit test harness
                        new RuntimePermission("accessDeclaredMembers"),
                        new PropertyPermission("*", "read"),
                        new java.io.FilePermission("<<ALL FILES>>", "read"));
    }

    /**
     * Sleeps until the given time has elapsed. Throws AssertionFailedError if interrupted.
     */
    void sleep(long millis)
    {
        try
        {
            delay(millis);
        }
        catch (InterruptedException ie)
        {
            AssertionFailedError afe = new AssertionFailedError("Unexpected InterruptedException");
            afe.initCause(ie);
            throw afe;
        }
    }

    /**
     * Spin-waits up to the specified number of milliseconds for the given thread to enter a wait
     * state: BLOCKED, WAITING, or TIMED_WAITING.
     */
    void waitForThreadToEnterWaitState(Thread thread, long timeoutMillis)
    {
        long startTime = System.nanoTime();
        for (; ; )
        {
            Thread.State s = thread.getState();
            if (s == Thread.State.BLOCKED || s == Thread.State.WAITING || s == Thread.State.TIMED_WAITING)
                return;
            else if (s == Thread.State.TERMINATED) fail("Unexpected thread termination");
            else if (millisElapsedSince(startTime) > timeoutMillis)
            {
                threadAssertTrue(thread.isAlive());
                return;
            }
            Thread.yield();
        }
    }

    /**
     * Waits up to LONG_DELAY_MS for the given thread to enter a wait state: BLOCKED, WAITING, or
     * TIMED_WAITING.
     */
    void waitForThreadToEnterWaitState(Thread thread)
    {
        waitForThreadToEnterWaitState(thread, LONG_DELAY_MS);
    }

    /**
     * Returns the number of milliseconds since time given by startNanoTime, which must have been
     * previously returned from a call to {@link System#nanoTime()}.
     */
    long millisElapsedSince(long startNanoTime)
    {
        return NANOSECONDS.toMillis(System.nanoTime() - startNanoTime);
    }

    /**
     * Returns a new started daemon Thread running the given runnable.
     */
    Thread newStartedThread(Runnable runnable)
    {
        Thread t = new Thread(runnable);
        t.setDaemon(true);
        t.start();
        return t;
    }

    /**
     * Waits for the specified time (in milliseconds) for the thread to terminate (using {@link
     * Thread#join(long)}), else interrupts the thread (in the hope that it may terminate later) and
     * fails.
     */
    void awaitTermination(Thread t, long timeoutMillis)
    {
        try
        {
            t.join(timeoutMillis);
        }
        catch (InterruptedException ie)
        {
            threadUnexpectedException(ie);
        }
        finally
        {
            if (t.getState() != Thread.State.TERMINATED)
            {
                t.interrupt();
                fail("Test timed out");
            }
        }
    }

    /**
     * Waits for LONG_DELAY_MS milliseconds for the thread to terminate (using {@link
     * Thread#join(long)}), else interrupts the thread (in the hope that it may terminate later) and
     * fails.
     */
    void awaitTermination(Thread t)
    {
        awaitTermination(t, LONG_DELAY_MS);
    }

    // Some convenient Runnable classes

    public abstract class CheckedRunnable implements Runnable
    {
        protected abstract void realRun() throws Throwable;

        @Override
        public final void run()
        {
            try
            {
                realRun();
            }
            catch (Throwable t)
            {
                threadUnexpectedException(t);
            }
        }
    }

    public abstract class RunnableShouldThrow implements Runnable
    {
        protected abstract void realRun() throws Throwable;

        final Class<?> exceptionClass;

        <T extends Throwable> RunnableShouldThrow(Class<T> exceptionClass)
        {
            this.exceptionClass = exceptionClass;
        }

        @Override
        public final void run()
        {
            try
            {
                realRun();
                threadShouldThrow(exceptionClass.getSimpleName());
            }
            catch (Throwable t)
            {
                if (!exceptionClass.isInstance(t)) threadUnexpectedException(t);
            }
        }
    }

    public abstract class ThreadShouldThrow extends Thread
    {
        protected abstract void realRun() throws Throwable;

        final Class<?> exceptionClass;

        <T extends Throwable> ThreadShouldThrow(Class<T> exceptionClass)
        {
            this.exceptionClass = exceptionClass;
        }

        @Override
        public final void run()
        {
            try
            {
                realRun();
                threadShouldThrow(exceptionClass.getSimpleName());
            }
            catch (Throwable t)
            {
                if (!exceptionClass.isInstance(t)) threadUnexpectedException(t);
            }
        }
    }

    public abstract class CheckedInterruptedRunnable implements Runnable
    {
        protected abstract void realRun() throws Throwable;

        @Override
        public final void run()
        {
            try
            {
                realRun();
                threadShouldThrow("InterruptedException");
            }
            catch (InterruptedException success)
            {
                threadAssertFalse(Thread.interrupted());
            }
            catch (Throwable t)
            {
                threadUnexpectedException(t);
            }
        }
    }

    public abstract class CheckedCallable<T> implements Callable<T>
    {
        protected abstract T realCall() throws Throwable;

        @Override
        public final T call()
        {
            try
            {
                return realCall();
            }
            catch (Throwable t)
            {
                threadUnexpectedException(t);
                return null;
            }
        }
    }

    public abstract class CheckedInterruptedCallable<T> implements Callable<T>
    {
        protected abstract T realCall() throws Throwable;

        @Override
        public final T call()
        {
            try
            {
                T result = realCall();
                threadShouldThrow("InterruptedException");
                return result;
            }
            catch (InterruptedException success)
            {
                threadAssertFalse(Thread.interrupted());
            }
            catch (Throwable t)
            {
                threadUnexpectedException(t);
            }
            return null;
        }
    }

    public static class NoOpRunnable implements Runnable
    {
        @Override
        public void run()
        {
        }
    }

    public static class NoOpCallable implements Callable
    {
        @Override
        public Object call()
        {
            return Boolean.TRUE;
        }
    }

    public static final String TEST_STRING = "a test string";

    public static class StringTask implements Callable<String>
    {
        @Override
        public String call()
        {
            return TEST_STRING;
        }
    }

    public Callable<String> latchAwaitingStringTask(final CountDownLatch latch)
    {
        return new CheckedCallable<String>()
        {
            @Override
            protected String realCall()
            {
                try
                {
                    latch.await();
                }
                catch (InterruptedException quittingTime)
                {
                }
                return TEST_STRING;
            }
        };
    }

    public Runnable awaiter(final CountDownLatch latch)
    {
        return new CheckedRunnable()
        {
            @Override
            public void realRun() throws InterruptedException
            {
                await(latch);
            }
        };
    }

    public void await(CountDownLatch latch)
    {
        try
        {
            assertTrue(latch.await(LONG_DELAY_MS, MILLISECONDS));
        }
        catch (Throwable t)
        {
            threadUnexpectedException(t);
        }
    }

    public void await(Semaphore semaphore)
    {
        try
        {
            assertTrue(semaphore.tryAcquire(LONG_DELAY_MS, MILLISECONDS));
        }
        catch (Throwable t)
        {
            threadUnexpectedException(t);
        }
    }

    //     /**
    //      * Spin-waits up to LONG_DELAY_MS until flag becomes true.
    //      */
    //     public void await(AtomicBoolean flag) {
    //         await(flag, LONG_DELAY_MS);
    //     }

    //     /**
    //      * Spin-waits up to the specified timeout until flag becomes true.
    //      */
    //     public void await(AtomicBoolean flag, long timeoutMillis) {
    //         long startTime = System.nanoTime();
    //         while (!flag.get()) {
    //             if (millisElapsedSince(startTime) > timeoutMillis)
    //                 throw new AssertionFailedError("timed out");
    //             Thread.yield();
    //         }
    //     }

    public static class NPETask implements Callable<String>
    {
        @Override
        public String call()
        {
            throw new NullPointerException();
        }
    }

    public static class CallableOne implements Callable<Integer>
    {
        @Override
        public Integer call()
        {
            return one;
        }
    }

    public class ShortRunnable extends CheckedRunnable
    {
        @Override
        protected void realRun() throws Throwable
        {
            delay(SHORT_DELAY_MS);
        }
    }

    public class ShortInterruptedRunnable extends CheckedInterruptedRunnable
    {
        @Override
        protected void realRun() throws InterruptedException
        {
            delay(SHORT_DELAY_MS);
        }
    }

    public class SmallRunnable extends CheckedRunnable
    {
        @Override
        protected void realRun() throws Throwable
        {
            delay(SMALL_DELAY_MS);
        }
    }

    public class SmallPossiblyInterruptedRunnable extends CheckedRunnable
    {
        @Override
        protected void realRun()
        {
            try
            {
                delay(SMALL_DELAY_MS);
            }
            catch (InterruptedException ok)
            {
            }
        }
    }

    public class SmallCallable extends CheckedCallable
    {
        @Override
        protected Object realCall() throws InterruptedException
        {
            delay(SMALL_DELAY_MS);
            return Boolean.TRUE;
        }
    }

    public class MediumRunnable extends CheckedRunnable
    {
        @Override
        protected void realRun() throws Throwable
        {
            delay(MEDIUM_DELAY_MS);
        }
    }

    public class MediumInterruptedRunnable extends CheckedInterruptedRunnable
    {
        @Override
        protected void realRun() throws InterruptedException
        {
            delay(MEDIUM_DELAY_MS);
        }
    }

    public Runnable possiblyInterruptedRunnable(final long timeoutMillis)
    {
        return new CheckedRunnable()
        {
            @Override
            protected void realRun()
            {
                try
                {
                    delay(timeoutMillis);
                }
                catch (InterruptedException ok)
                {
                }
            }
        };
    }

    public class MediumPossiblyInterruptedRunnable extends CheckedRunnable
    {
        @Override
        protected void realRun()
        {
            try
            {
                delay(MEDIUM_DELAY_MS);
            }
            catch (InterruptedException ok)
            {
            }
        }
    }

    public class LongPossiblyInterruptedRunnable extends CheckedRunnable
    {
        @Override
        protected void realRun()
        {
            try
            {
                delay(LONG_DELAY_MS);
            }
            catch (InterruptedException ok)
            {
            }
        }
    }

    /**
     * For use as ThreadFactory in constructors
     */
    public static class SimpleThreadFactory implements ThreadFactory
    {
        @Override
        public Thread newThread(Runnable r)
        {
            return new Thread(r);
        }
    }

    public interface TrackedRunnable extends Runnable
    {
        boolean isDone();
    }

    public static TrackedRunnable trackedRunnable(final long timeoutMillis)
    {
        return new TrackedRunnable()
        {
            private volatile boolean done = false;

            @Override
            public boolean isDone()
            {
                return done;
            }

            @Override
            public void run()
            {
                try
                {
                    delay(timeoutMillis);
                    done = true;
                }
                catch (InterruptedException ok)
                {
                }
            }
        };
    }

    public static class TrackedShortRunnable implements Runnable
    {
        public volatile boolean done = false;

        @Override
        public void run()
        {
            try
            {
                delay(SHORT_DELAY_MS);
                done = true;
            }
            catch (InterruptedException ok)
            {
            }
        }
    }

    public static class TrackedSmallRunnable implements Runnable
    {
        public volatile boolean done = false;

        @Override
        public void run()
        {
            try
            {
                delay(SMALL_DELAY_MS);
                done = true;
            }
            catch (InterruptedException ok)
            {
            }
        }
    }

    public static class TrackedMediumRunnable implements Runnable
    {
        public volatile boolean done = false;

        @Override
        public void run()
        {
            try
            {
                delay(MEDIUM_DELAY_MS);
                done = true;
            }
            catch (InterruptedException ok)
            {
            }
        }
    }

    public static class TrackedLongRunnable implements Runnable
    {
        public volatile boolean done = false;

        @Override
        public void run()
        {
            try
            {
                delay(LONG_DELAY_MS);
                done = true;
            }
            catch (InterruptedException ok)
            {
            }
        }
    }

    public static class TrackedNoOpRunnable implements Runnable
    {
        public volatile boolean done = false;

        @Override
        public void run()
        {
            done = true;
        }
    }

    public static class TrackedCallable implements Callable
    {
        public volatile boolean done = false;

        @Override
        public Object call()
        {
            try
            {
                delay(SMALL_DELAY_MS);
                done = true;
            }
            catch (InterruptedException ok)
            {
            }
            return Boolean.TRUE;
        }
    }

    //     /**
    //      * Analog of CheckedRunnable for RecursiveAction
    //      */
    //     public abstract class CheckedRecursiveAction extends RecursiveAction {
    //         protected abstract void realCompute() throws Throwable;

    //         public final void compute() {
    //             try {
    //                 realCompute();
    //             } catch (Throwable t) {
    //                 threadUnexpectedException(t);
    //             }
    //         }
    //     }

    //     /**
    //      * Analog of CheckedCallable for RecursiveTask
    //      */
    //     public abstract class CheckedRecursiveTask<T> extends RecursiveTask<T> {
    //         protected abstract T realCompute() throws Throwable;

    //         public final T compute() {
    //             try {
    //                 return realCompute();
    //             } catch (Throwable t) {
    //                 threadUnexpectedException(t);
    //                 return null;
    //             }
    //         }
    //     }

    /**
     * For use as RejectedExecutionHandler in constructors
     */
    public static class NoOpREHandler implements RejectedExecutionHandler
    {
        @Override
        public void rejectedExecution(Runnable r, ThreadPoolExecutor executor)
        {
        }
    }

    /**
     * A CyclicBarrier that uses timed await and fails with AssertionFailedErrors instead of throwing
     * checked exceptions.
     */
    public class CheckedBarrier extends CyclicBarrier
    {
        public CheckedBarrier(int parties)
        {
            super(parties);
        }

        @Override
        public int await()
        {
            try
            {
                return super.await(2 * LONG_DELAY_MS, MILLISECONDS);
            }
            catch (TimeoutException e)
            {
                throw new AssertionFailedError("timed out");
            }
            catch (Exception e)
            {
                AssertionFailedError afe = new AssertionFailedError("Unexpected exception: " + e);
                afe.initCause(e);
                throw afe;
            }
        }
    }

    void checkEmpty(BlockingQueue q)
    {
        try
        {
            assertTrue(q.isEmpty());
            assertEquals(0, q.size());
            assertNull(q.peek());
            assertNull(q.poll());
            assertNull(q.poll(0, MILLISECONDS));
            assertEquals("[]", q.toString());
            assertTrue(Arrays.equals(q.toArray(), new Object[0]));
            assertFalse(q.iterator().hasNext());
            try
            {
                q.element();
                shouldThrow();
            }
            catch (NoSuchElementException success)
            {
            }
            try
            {
                q.iterator().next();
                shouldThrow();
            }
            catch (NoSuchElementException success)
            {
            }
            try
            {
                q.remove();
                shouldThrow();
            }
            catch (NoSuchElementException success)
            {
            }
        }
        catch (InterruptedException ie)
        {
            threadUnexpectedException(ie);
        }
    }

    @SuppressWarnings("unchecked")
    <T> T serialClone(T o)
    {
        try
        {
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(bos);
            oos.writeObject(o);
            oos.flush();
            oos.close();
            ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bos.toByteArray()));
            T clone = (T) ois.readObject();
            assertSame(o.getClass(), clone.getClass());
            return clone;
        }
        catch (Throwable t)
        {
            threadUnexpectedException(t);
            return null;
        }
    }
}
